Leukosis

Bovine Leukosis is a disease caused by the Bovine Leukosis virus (BLV).  This is a blood borne disease that dwells in the lymphocytes (white blood cells) in cattle. Only 5% of infected animals will exhibit the clinical symptoms of developing tumors in lymphatic tissue. The prevalence of leukosis is wide spread. It is fairly common to find herds with a prevalence of 80-90%, however not very common to find herds that are completely free of leukosis. According to the NAHMS ’96 study, 88.5% of dairy herds and 38.7% of beef herds are infected. Transmission occurs by the transfer of bodily fluids that contain infected white cells (blood, colostrum, milk). Anything from reusing without sanitizing contaminated needles, syringes, breeding sleeves, dehorners, or balling guns can transmit leukosis. Transmission can also occur through colostrum or to a fetus in utero.

The biggest loss for dairy producers is typically associated with lost cattle marketing opportunities, sale of replacement stock, bulls to A.I. or embryos. Other economic losses related to slaughter value, culling rates, and reproductive performance are often perceived fairly minor since so few cows become clinically infected.

However, if you are curious as to what the level of leukosis is in your herd or want to start reducing the spread of leukosis, Minnesota DHIA now offers the Milk ELISA Leukosis test. It can be run on the regular testday milk sample for $6 per sample. Results are back to you typically in less than one week. If you would like to do a whole herd bulk tank screening, one positive cow can be detected in a herd up to 125 cows.  

Optimal testing protocol:

n Test all cattle in a herd to establish a prevalence

n Test all cattle entering the herd and isolate them for 30-60 days, test again prior to introduction into the herd

n Develop and implement management procedures to reduce spread of disease

n Establish annual testing program for all animals in the herd

BVD Testing

Bovine Viral Diarrhea (BVD) is a fluid/aerosol borne disease in ruminants. For cattle producers the virus causes economic losses through decreased weight gains, decreased milk production, reproductive losses, and death with costs estimated from $24 to $200 per cow per year. There are two categories of BVD infection: Acute and Persistent. Acute infections occur after birth and are transferred by infected fluids, contaminated equipment, or animal contact. Nearly 95% of BVD infections are acute. Persistent infections occur in utero. Typically only 10% of persistent infected animals survive over 2 years of age. These animals will continuously shed the virus becoming the major source of spreading the disease to other animals and other farms. Approximately 10-15% of US dairies have some incidence of BVD.

Characteristics of high risk BVD herds:

n Poor reproductive performance and abortions

n Poor calf performance

n Lingering respiratory challenges

n No vaccination program

n Frequent cattle movement

BVD analysis can be done on the regular testday milk sample. Samples can be run on individual cows at $6 per sample or bulk tanks at $40 per sample. The PCR can detect a single positive cow in a bulk tank sample up to 250 cows. If your tank sample result is positive, you may want to pooling samples of individual cows. Please contact a lab manager for further information and pricing on pooling samples. Muril Niebuhr, Zumbrota Lab 507.732.5880  OR   Mark Heidgerken, Stearns DHIA Laboratory 1.800.369.2697.